US Patent 7468298 Method of manufacturing flash memory device

A method of manufacturing a flash memory device, wherein, when a first polysilicon layer is formed, a doped polysilicon layer and an amorphous polysilicon layer are formed so that they are laminated. A process of forming a sidewall oxide film and an oxide film and a thermal treatment process are performed to form the profile of the first polysilicon layer negatively. It is therefore possible to prevent the remnants of the first polysilicon layer below the isolation film. Accordingly, a failure in which the floating gates adjacent in the direction of the isolation film are connected by the remnants of the first polysilicon layer can be prevented.